In clinical practice brachytherapy application are gaining importance. In the course of a brachytherapy treatment a radioactive source, usually a gamma emitter, is introduced into a target volume of a patient. The radioactive source may be introduced manually or using an afterloader device. Generally, the afterloader device is used for providing the radioactive source or sources inside the patient for a given (short) period of time inside pre-positioned catheters. In such a case, the gamma source may be a high dose rate source or a low dose rate source. Alternatively, the sources (seeds) may be provided inside the target volume of the patient for a prolonged (several hours) or permanent dwelling. Such sources may be low dose rate sources.
It is a disadvantage of the contemporary brachytherapy that the actual source position inside the volume is verified indirectly. For example, generally suitable X-ray imaging may be used for determining the position of the source bodies inside the patient (or a catheter introduced inside the patient). However, such approach may be not sufficiently accurate or reliable in certain circumstances, for instance when a train of sources is being provided, the active rods being interleaved with non-active spacers.